testing: rename t.TempDir to t.Mkdir

[rogpeppe]

The originally proposed name for testing.T.TempDir was Mkdir. The name was changed during the proposal process. There has been some confusion about the intended semantics: is it more like ioutil.TempDir or os.TempDir ?

To avoid the confusion, I suggest that we use the originally proposed name, Mkdir. It's then very clear that the method is creating a new directory. The fact that the method has no arguments is a clear indication that the directory name is chosen by the method itself rather than by the caller.

[mvdan]

I was initially against this name, because I thought testing.T.Mkdir could be confused for os.Mkdir. But Roger correctly pointed out that's very unlikely, since testing.T.Mkdir does not take any arguments.

[gopherbot]

Change https://golang.org/cl/234558 mentions this issue: testing: rename TempDir to Mkdir

[rsc]

Mkdir does not convey "this is temporary". (It's not ioutil.Mkdir.) Let's leave it as TempDir. I understand the conflict with os.TempDir, but more people know about ioutil.TempDir anyway. Thanks.

[rogpeppe]

Fair enough. Will close.